ST10F269ZX datasheet(109/184 Pages) STMICROELECTRONICS

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ST10F269

16 - REAL TIME CLOCK

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When RTCD increments to reach 00000h, The 20-bit word stored into RTCPH, RTCPL registers is loaded

in RTCD.

Bit 15 to bit 4 of RTCPH and RTCDH are not

used. When reading, the return value of those bit

will be zeros.

16.1.4 - RTCH & RTCL: RTC Programmable

COUNTER Registers

The RTC has 2 x 16-bit programmable counters

which count rate is based on the basic time

reference (for example 1 second). As the clock

oscillator may be kept working, even in power

down mode, the RTC counters may be used as a

system clock. In addition RTC counters and

registers are not modified at any system reset.

The only way to force their value is to write them

via the XBUS.

Those counters are write protected as well. The

bit RTOFF of the RTCCON register must be set

(RTC dividers and counters are stopped) to

enable a write operation on RTCH or RTCL.

A write operation on RTCH or RTCL register loads

directly the corresponding counter. When reading,

the current value in the counter (system date) is

returned.

The counters keeps on running while the clock

oscillator is working.

RTCL (EC0Eh)

XBUS

Reset Value: XXXXh

RTCH (EC10h)

XBUS

Reset Value: XXXXh

Note: Those registers are nor reset

Figure 53 : DIVIDER Counters

11 10 9

15 14 13 12

RTCDH

RTCDL

11 10 9

15 14 13 12

19 18 17 16

20 bit word internal value of the Prescaler divider

9876543210

RTCL

9876543210

RTCH

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